Diff viewer - Don't zoom out the geometry windows when changing the diff type.

[SrNetoChan]

Is your feature request related to a problem? Please describe. Some time one needs to use different diff types to check the introduced changes. Currently, every time you change the diff type, the window will zoom out to extent of the geometry, making you loose the area that you were inspecting

Describe the solution you'd like It would be nicer not to trigger the zoom to feature extent when the diff type is changes. If needed a new button on context menu could be added to perform that zoom to extent.